Techniques for composite media storage and retrieval

ABSTRACT

One embodiment sets forth a technique that includes receiving a request for a range of data included in an encoded version of the media title that is stored across a set of files. The technique also includes determining, based on a file extent index, one or more files included in the set of files, wherein the file extent index maps an identifier for each file in the set to a given range of data that is stored in the file and included in the encoded version. The technique further includes retrieving the range of data from the file(s), wherein at least a portion of the retrieved range of data falls within the given range of data that is stored in each of the one or more files, and transmitting the range of data in a response to the request.

BACKGROUND Field of the Various Embodiments

Embodiments of the present disclosure relate generally to computerscience and computer networks for streaming media, and morespecifically, to techniques for composite media storage and retrieval.

DESCRIPTION OF THE RELATED ART

A video streaming service is typically designed to provide users withaccess to one or more libraries of various media titles. To access agiven media title, a user usually connects to the video streamingservice via an endpoint device, such as a laptop computer, smarttelevision, tablet computer, or similar device. The user can then selectthe given media title via a graphical user interface (GUI) that isdisplayed on the endpoint device and configured to allow users to makeselections from one or more libraries of media titles. Upon selectingthe given media title, the server machines that host the media titlestream media content associated with the media title to the endpointdevice. The media content generally includes frames of video, subtitle,and/or audio data encoded with specific bitrates, encoding formats,and/or other encoding settings. These encoding settings may additionallybe varied in the streamed media content based on network conditions,user preferences, and/or other parameters. A streaming applicationexecuting on the endpoint device can request these frames as ranges ofbyte and/or time offsets from the server machines. While a given rangeof media content in the media title is played on the endpoint device,the streaming application can request and receive the next range ofmedia content from the server machines to allow playback of the mediatitle to proceed without interruption.

In various streaming service implementations, different versions of agiven media title oftentimes are streamed to different endpoint devicesto accommodate content differences that exist in a given scene or otherportion of the media title. For example, a feature-length film couldinclude a number of scenes with on-screen text that provides informationabout the characters in the film, messages sent or received by variouscharacters, content viewed by a given character on a computer or mobiledevice, or additional context for viewers of the film. Such on-screentext typically would be shown in the language spoken by the charactersin the film and would be “burned” into the film (instead of beingincluded in subtitles) to allow the production team to control theplacement, font, size, and overall “look” of the text within the film.In such a scenario, each language into which the film is dubbed wouldrequire a different set of these particular scenes with localizedon-screen text, thereby resulting in different versions of the film.

Some legacy streaming applications are able to retrieve and playbackonly a single version of a media title from start to finish, instead ofswitching between versions at certain points during playback of a givenmedia title. Continuing with the above example, a legacy streamingapplication could switch between files within an adaptive bitrate (ABR)ladder for a “playback title” representing a language-specific versionof the film, but would not be able to switch between a first playbacktitle that includes non-localized video content in the film and a secondplayback title that includes localized versions of a subset of videocontent in the film unless a user stopped playback of the film, manuallychanged the language setting for the film within the legacy streamingapplication, and subsequently resumed playback of the film with the newlanguage setting.

To accommodate these types of legacy streaming applications, a videostreaming service may serve each version of a given media title using aseparate file, which includes all of the video content required forcomplete playback of that version of the media title. Continuing withthe above example, a feature-length film could include twenty scenes (orportions of scenes) with localized on-screen text, which could take upless than ten minutes of screen time out of a total runtime of more thanthree hours. The film also could have thirty localized versions of thesescenes (or portions of scenes) to handle on-screen text in thirtydifferent languages across all encoding bitrates and formats. Each setof localized scenes for a given language could then be packaged with thenon-localized scenes in the film to produce a single localized file fora given combination of language, encoding bitrate, and encoding formatthat can be retrieved and played end-to-end using a legacy streamingapplication.

One drawback of the above approach, however, is that storing full copiesof individual versions of media titles to accommodate requests fromlegacy streaming applications involves duplicating video content that iscommon to multiple versions of the media title, which can consumesubstantial computational and storage resources. Continuing with theabove example, the non-localized scenes in a feature-length film couldconsume 400 gigabytes (GB) of space across the set of encoding bitratesand formats, while a given set of localized scenes (or portions ofscenes) needed across all of these encoding bitrates and formats couldconsume less than a few GB of space. Using the above approach, the smallnumber of localized scenes specific to a given localized version of thefilm would be encoded and packaged with the non-localized video contentinto each video file. For thirty different languages, as in the aboveexample, more than twelve terabytes (TB) of video content would have tobe encoded and stored on various server machines to support all thirtylocalized versions of the film, even though the vast majority of thevideo content would be identical across the different localizedversions.

As the foregoing illustrates, what is needed in the art are moreeffective techniques for storing and retrieving video content forstreaming to endpoint devices.

SUMMARY

One embodiment sets forth a technique for accessing a media title forplayback. The technique includes receiving from a client device a firstrequest for a first range of data included in a first encoded version ofthe media title, wherein the first encoded version of the media title isstored across a first set of files. The technique also includesdetermining, based on a first file extent index, one or more files thatare included in the first set of files and from which the first range ofdata is to be accessed, wherein, for each file included in the first setof files, the first file extent index maps an identifier for the file toa given range of data that is stored in the file and that is included inthe first encoded version of the media title. The technique furtherincludes retrieving the first range of data from the one or more files,wherein at least a portion of the first range of data retrieved fromeach of the one or more files falls within the given range of data thatis stored in the file. The technique further includes transmitting thefirst range of data to the client device in a response to the firstrequest.

One technical advantage of the disclosed techniques relative to theprior art is that, with the disclosed techniques, duplication of videocontent across multiple versions of a media title is reduced. In thatregard, the disclosed techniques enable a single copy of video contentthat is common to all versions of a given film to be stored, instead ofreplicating identical video content across multiple files. Thus, withthe disclosed techniques, fewer computational and storage resources areconsumed when encoding and storing multiple versions of a media titlefor streaming. Another technical advantage of the disclosed techniquesrelative to the prior art is that the disclosed techniques allow a givenversion of the media title to be created or modified in an efficient,modular manner, unlike prior art approaches that encode and package agiven version of a media title from beginning to end. These technicaladvantages provide one or more technological advancements over prior artapproaches.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the variousembodiments can be understood in detail, a more particular descriptionof the inventive concepts, briefly summarized above, may be had byreference to various embodiments, some of which are illustrated in theappended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments of the inventive conceptsand are therefore not to be considered limiting of scope in any way, andthat there are other equally effective embodiments.

FIG. 1 illustrates a network infrastructure configured to implement oneor more aspects of the various embodiments.

FIG. 2 is a block diagram of a content server that may be implemented inconjunction with the network infrastructure of FIG. 1, according tovarious embodiments.

FIG. 3 is a block diagram of a control server that may be implemented inconjunction with the network infrastructure of FIG. 1, according tovarious embodiments.

FIG. 4 is a block diagram of an endpoint device that may be implementedin conjunction with the network infrastructure of FIG. 1, according tovarious embodiments.

FIG. 5 illustrates how a request for media content is processed by theserver application of FIG. 2, according to various embodiments.

FIG. 6A illustrates an exemplar set of data structures that can be usedwhen playing back a version of a media title, according to variousembodiments.

FIG. 6B illustrates how a request for media content is processed usingthe exemplar set of data structures of FIG. 6A, according to variousembodiments.

FIG. 7 is a flow diagram of method steps for accessing a media title forplayback, according to various embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a more thorough understanding of the various embodiments.However, it will be apparent to one skilled in the art that theinventive concepts may be practiced without one or more of thesespecific details.

A video streaming service delivers high-quality digital video content,such as movies and television shows, to viewers. To support legacy videostreaming applications that play streaming content from beginning to endwithin a single video, different versions of a given media title can bestored in their entirety within different files. Each file can include aportion of video content that is specific to the corresponding versionof the media title, as well as a (usually much larger) portion of videocontent that is the same across multiple versions of the media title. Asdescribed herein, a “file” includes video content encoded at differentbitrates to support adaptive bitrate (ABR) streaming of thecorresponding version of the media title. A legacy streaming applicationthen plays a version of the media title by continuously requestingcontiguous ranges of byte and/or time offsets from the video streamingservice starting at the beginning of the corresponding file, playing therequested ranges of content in the order in which the ranges werereceived, and discontinuing playback when the end of the file isreached.

For example, a video streaming service could offer 30 differentlocalized versions of a feature length film. Each version of the featurelength film could be dubbed with a corresponding language and includeone or more scenes with on-screen text in that language. This on-screentext could provide information about the characters in the film,messages sent or received by various characters, content viewed by agiven character on a computer or mobile device, or additional contextfor viewers of the film. Such on-screen text typically would be shown inthe language spoken by the characters in the film and would be “burned”into the film (instead of being included in subtitles) to allow theproduction team to control the placement, font, size, and overall “look”of the text within the film. The localized scenes with on-screen textwould traditionally be packaged with remaining scenes in the film toproduce a single localized file for each localized version, which can beretrieved and played end-to-end on a legacy streaming video application.A server that delivers the film in multiple languages to client deviceswould therefore store multiple files that could occupy multiple TB ofstorage, even though the vast majority of the video content in the filesis the same.

To reduce resource overhead associated with encoding and storingduplicated content in different versions of a media title, the disclosedtechniques store content related to multiple versions of the media titlein one or more “component” files and/or segments within each file. Thesefiles include a single copy of each version of a scene (or anotherportion of video content) in the media title instead of replicatingidentical video content across multiple files. For example, a “base”version of a film that includes video content in the original languageof the film could be stored in a single file. Localized versions ofscenes (or other portions of video content) in the film could then bestored in multiple other files, where each file includes one or moredata segments that store localized video content for a correspondinglocalized version of the film and each data segment includes a“component” of the localized video content (e.g., a consecutive numberof seconds or minutes of video in the film). In another example, asingle file could store the “base” version of the film as well as alllocalized versions of video content in the film. In a third example, afirst file could store the “base” version of the film, and a second filecould store all localized versions of video content in the film.

The disclosed techniques also use a number of index structures with thefiles or segments to process requests from streaming video applicationsfor content from the media title. The index structures include a numberof file mappings that map identifiers for files that store video contentfor the media title to paths that can be used to locate the files in afilesystem. The index structures also include a file extent index thatis used to retrieve video content for a given version of the media titlewhen the video content is stored across multiple files and/or multiplenon-contiguous segments within the same file. The file extent indexincludes an identifier for the corresponding version of the media title,metadata related to the version, and identifiers for files storing videocontent that is included in the version. Within the file extent index,each identifier for a file is mapped to a range of offsets in the file.The range of offsets represents a portion of video content that is to beretrieved from the file during playback of the version. The ordering ofmappings between file identifiers and the corresponding ranges ofoffsets in the file extent index additionally reflects the order inwhich video content should be retrieved for end-to-end playback of theversion of the media title.

For example, the file extent index for a French version of a film couldinclude a first identifier for the French version followed by threemappings. The mappings include a first mapping between a secondidentifier for an English “base” version of the film and a first rangeof byte offsets in a first file that includes the base version, followedby a second mapping between a third identifier for a second file thatincludes French versions of one or more scenes in the film and a secondrange of byte offsets in the second file, followed by a third mappingbetween the second identifier and a third range of byte offsets in thefirst file. During end-to-end playback of the French version of thefilm, a legacy streaming video application would request consecutiveranges of bytes of video content from a virtual “file” represented bythe first identifier for the French version. A server would process therequests by matching the first identifier to the file extent index andusing the mappings in the file extent to return data from the firstrange of byte offsets in the first file, followed by data from thesecond range of byte offsets in the second file, followed by data fromthe third range of byte offsets in the first file. In other words, theserver would use the file extent index to piece together differentranges of data from multiple files and return the data in response tothe requests, so that the data appears to be read in contiguous “chunks”from the same file from the perspective of the legacy streaming videoapplication.

The index structures further include a segment index that converts timeoffsets into byte offsets within a given file. This segment index can beused to process requests for video content that is specified in terms oftime offset ranges (instead of byte offset ranges). These types ofrequests can be issued by a streaming video application to perform a“scrub” or “seek” operation that changes the point in time at which themedia title is played.

In some embodiments, the index structures can be used to efficientlycreate a new version of the media title and/or modify an existingversion of the media title. For example, a new version of a film couldbe added to a video streaming service by populating one or more newfiles with video content that is specific to the new version, mapping anidentifier for each new file to the path for the new file, and creatinga new file extent index that includes mappings to byte ranges spanned bythe video content in the new file(s) and additional mappings to byteranges spanned by video content in one or more other files that includea “base” version of the film. The new file extent index could include afirst mapping of a first file identifier to a first range of dataspanned by a replacement version of a scene in the new version of thefilm instead of a second mapping of a second file identifier to a secondrange of data spanned by an original version of the scene from the“base” version of the film. During playback of the new version on anendpoint device, a server would process requests for ranges of contentin the new version from the endpoint device using the new file extentindex. Because the new file extent index causes the server to returndata from the replacement version of the scene instead of from theoriginal version of the scene, the new file(s) and new file extent indexallow the original version of the scene to be substituted with thereplacement version.

One technical advantage of the disclosed techniques relative to theprior art is that, with the disclosed techniques, duplication of videocontent across multiple versions of a media title is reduced. In thatregard, the disclosed techniques enable a single copy of video contentthat is common to all versions of a given film to be stored, instead ofreplicating identical video content across multiple files. Thus, withthe disclosed techniques, fewer computational and storage resources areconsumed when encoding and storing multiple versions of a media titlefor streaming. Another technical advantage of the disclosed techniquesrelative to the prior art is that the disclosed techniques allow a givenversion of the media title to be created or modified in an efficient,modular manner, unlike prior art approaches that encode and package agiven version of a media title from beginning to end. These technicaladvantages provide one or more technological advancements over prior artapproaches.

System Overview

FIG. 1 illustrates a network infrastructure configured to implement oneor more aspects of the various embodiments. As shown, networkinfrastructure 100 includes one or more content servers 110, a controlserver 120, and one or more endpoint devices 115, which are connected toone another and/or one or more cloud services 130 via a communicationsnetwork 105. Network infrastructure 100 is generally used to distributecontent to content servers 110 and endpoint devices 115.

Each endpoint device 115 communicates with one or more content servers110 (also referred to as “caches” or “nodes”) via network 105 todownload content, such as textual data, graphical data, audio data,video data, and other types of data. The downloadable content, alsoreferred to herein as a “file,” is then presented to a user of one ormore endpoint devices 115. In various embodiments, endpoint devices 115may include computer systems, set top boxes, mobile computer,smartphones, tablets, console and handheld video game systems, digitalvideo recorders (DVRs), DVD players, connected digital TVs, dedicatedmedia streaming devices, (e.g., the Roku® set-top box), and/or any othertechnically feasible computing platform that has network connectivityand is capable of presenting content, such as text, images, video,and/or audio content, to a user.

Network 105 includes any technically feasible wired, optical, wireless,or hybrid network that transmits data between or among content servers110, control server 120, endpoint device 115, cloud services 130, and/orother components. For example, network 105 could include a wide areanetwork (WAN), local area network (LAN), personal area network (PAN),WiFi network, cellular network, Ethernet network, Bluetooth network,universal serial bus (USB) network, satellite network, and/or theInternet.

Each content server 110 may include one or more applications configuredto communicate with control server 120 to determine the location andavailability of various files that are tracked and managed by controlserver 120. Each content server 110 may further communicate with cloudservices 130 and one or more other content servers 110 to “fill” eachcontent server 110 with copies of various files. In addition, contentservers 110 may respond to requests for files received from endpointdevices 115. The files may then be distributed from content server 110or via a broader content distribution network. In some embodiments,content servers 110 may require users to authenticate (e.g., using ausername and password) before accessing files stored on content servers110. Although only a single control server 120 is shown in FIG. 1, invarious embodiments multiple control servers 120 may be implemented totrack and manage files.

In various embodiments, cloud services 130 may include an online storageservice (e.g., Amazon® Simple Storage Service, Google® Cloud Storage,etc.) in which a catalog of files, including thousands or millions offiles, is stored and accessed in order to fill content servers 110.Cloud services 130 also may provide compute or other processingservices. Although only a single instance of cloud services 130 is shownin FIG. 1, in various embodiments multiple cloud services 130 and/orcloud service instances may be implemented.

FIG. 2 is a block diagram of content server 110 that may be implementedin conjunction with the network infrastructure of FIG. 1, according tovarious embodiments. As shown, content server 110 includes, withoutlimitation, a central processing unit (CPU) 204, a system disk 206, aninput/output (I/O) devices interface 208, a network interface 210, aninterconnect 212, and a system memory 214.

CPU 204 is configured to retrieve and execute programming instructions,such as a server application 217, stored in system memory 214.Similarly, CPU 204 is configured to store application data (e.g.,software libraries) and retrieve application data from system memory214. Interconnect 212 is configured to facilitate transmission of data,such as programming instructions and application data, between CPU 204,system disk 206, I/O devices interface 208, network interface 210, andsystem memory 214. I/O devices interface 208 is configured to receiveinput data from I/O devices 216 and transmit the input data to CPU 204via interconnect 212. For example, I/O devices 216 may include one ormore buttons, a keyboard, a mouse, and/or other input devices. I/Odevices interface 208 is further configured to receive output data fromCPU 204 via interconnect 212 and transmit the output data to I/O devices216.

System disk 206 may include one or more hard disk drives, solid statestorage devices, or similar storage devices. System disk 206 isconfigured to store non-volatile data such as files 218 (e.g., audiofiles, video files, subtitle files, application files, softwarelibraries, etc.). Files 218 can then be retrieved by one or moreendpoint devices 115 via network 105. In some embodiments, networkinterface 210 is configured to operate in compliance with the Ethernetstandard.

System memory 214 includes server application 217, which is configuredto service requests received from endpoint device 115 and other contentservers 110 for one or more files 218. When server application 217receives a request for a given file 218, server application 217retrieves the requested file 218 from system disk 206 and transmits file218 to an endpoint device 115 or a content server 110 via network 105.Files 218 include digital content items such as video files, audiofiles, and/or still images. In addition, files 218 may include metadataassociated with such content items, user/subscriber data, etc. Files 218that include visual content item metadata and/or user/subscriber datamay be employed to facilitate the overall functionality of networkinfrastructure 100. In alternative embodiments, some or all of files 218may instead be stored in a control server 120, or in any othertechnically feasible location within network infrastructure 100.

In one or more embodiments, server application 217 includesfunctionality to store video content that is unique to differentversions of a media title in multiple byte ranges within one or morefiles 218. Server application 217 also uses a number of index structuresand mappings to retrieve the byte ranges in a particular order for eachversion of the media title during playback of the version on one or moreendpoint devices 115. As described in further detail with respect toFIGS. 5-7, this technique for storing and retrieving content allowsserver application 217 to minimize duplication of content in files 218.This technique further allows server application 217 to return, inresponse to each request from endpoint devices 115 for content from agiven version of the media title, data that appears to be read incontiguous “chunks” from the same file, even when the data is storedacross multiple files 218.

FIG. 3 is a block diagram of control server 120 that may be implementedin conjunction with the network infrastructure 100 of FIG. 1, accordingto various embodiments. As shown, control server 120 includes, withoutlimitation, a central processing unit (CPU) 304, a system disk 306, aninput/output (I/O) devices interface 308, a network interface 310, aninterconnect 312, and a system memory 314.

CPU 304 is configured to retrieve and execute programming instructions,such as control application 317, stored in system memory 314. Similarly,CPU 304 is configured to store application data (e.g., softwarelibraries) and retrieve application data from system memory 314 and adatabase 318 stored in system disk 306. Interconnect 312 is configuredto facilitate transmission of data between CPU 304, system disk 306, I/Odevices interface 308, network interface 310, and system memory 314. I/Odevices interface 308 is configured to transmit input data and outputdata between I/O devices 316 and CPU 304 via interconnect 312. Systemdisk 306 may include one or more hard disk drives, solid state storagedevices, and the like. System disk 306 is configured to store a database318 of information associated with content servers 110, cloud services130, and files 218.

System memory 314 includes a control application 317 configured toaccess information stored in database 318 and process the information todetermine the manner in which specific files 218 will be replicatedacross content servers 110 included in the network infrastructure 100.Control application 317 may further be configured to receive and analyzeperformance characteristics associated with one or more of contentservers 110 and/or endpoint devices 115. As noted above, in someembodiments, metadata associated with such visual content items, and/oruser/subscriber data may be stored in database 318 rather than in files218 stored in content servers 110.

FIG. 4 is a block diagram of endpoint device 115 that may be implementedin conjunction with the network infrastructure of FIG. 1, according tovarious embodiments. As shown, endpoint device 115 may include, withoutlimitation, a CPU 410, a graphics subsystem 412, an I/O devicesinterface 414, a mass storage unit 416, a network interface 418, aninterconnect 422, and a memory subsystem 430.

In some embodiments, CPU 410 is configured to retrieve and executeprogramming instructions stored in memory subsystem 430. Similarly, CPU410 is configured to store and retrieve application data (e.g., softwarelibraries) residing in memory subsystem 430. Interconnect 422 isconfigured to facilitate transmission of data, such as programminginstructions and application data, between CPU 410, graphics subsystem412, I/O devices interface 414, mass storage unit 416, network interface418, and memory subsystem 430.

In some embodiments, graphics subsystem 412 is configured to generateframes of video data and transmit the frames of video data to displaydevice 450. In some embodiments, graphics subsystem 412 may beintegrated into an integrated circuit, along with CPU 410. Displaydevice 450 may comprise any technically feasible means for generating animage for display. For example, display device 450 may be fabricatedusing liquid crystal display (LCD) technology, cathode-ray technology,and light-emitting diode (LED) display technology. I/O devices interface414 is configured to receive input data from user I/O devices 452 andtransmit the input data to CPU 410 via interconnect 422. For example,user I/O devices 452 may include one or more buttons, a keyboard, and/ora mouse or other pointing device. I/O devices interface 414 alsoincludes an audio output unit configured to generate an electrical audiooutput signal. User I/O devices 452 includes a speaker configured togenerate an acoustic output in response to the electrical audio outputsignal. In alternative embodiments, display device 450 may include thespeaker. Examples of suitable devices known in the art that can displayvideo frames and generate an acoustic output include televisions,smartphones, smartwatches, electronic tablets, and the like.

A mass storage unit 416, such as a hard disk drive or flash memorystorage drive, is configured to store non-volatile data. A networkinterface 418 is configured to transmit and receive packets of data vianetwork 105. In some embodiments, network interface 418 is configured tocommunicate using the well-known Ethernet standard. Network interface418 is coupled to CPU 410 via interconnect 422.

In some embodiments, memory subsystem 430 includes programminginstructions and application data that include an operating system 432,a user interface 434, a playback application 436, and a platform player438. Operating system 432 performs system management functions such asmanaging hardware devices including network interface 418, mass storageunit 416, I/O devices interface 414, and graphics subsystem 412.Operating system 432 also provides process and memory management modelsfor user interface 434, playback application 436, and/or platform player438. User interface 434, such as a window and object metaphor, providesa mechanism for user interaction with endpoint device 115. Personsskilled in the art will recognize the various operating systems and userinterfaces that are well-known in the art and suitable for incorporationinto endpoint device 115.

In some embodiments, playback application 436 is configured to requestand receive content from content server 110 via network interface 418.Further, playback application 436 is configured to interpret the contentand present the content via display device 450 and/or user I/O devices452. In so doing, playback application 436 may generate frames of videodata based on the received content and then transmit those frames ofvideo data to platform player 438. In response, platform player 438causes display device 450 to output the frames of video data forplayback of the content on endpoint device 115. In one embodiment,platform player 438 is included in operating system 432.

Composite Media Storage and Retrieval

FIG. 5 illustrates how a request 500 for media content is processed byserver application 217 of FIG. 2, according to various embodiments. Asshown, request 500 includes an identifier 508 for a version of a mediatitle and a range 510 of data to retrieve from the version. For example,identifier 508 could include a title, filename, numeric identifier,and/or another value that uniquely identifies the version. Range 510could include a range of byte offsets, time offsets, and/or other typesof offsets in the version.

As mentioned above, each version of the media title may include a subsetof video content that is specific to the version, while a majority ofvideo content in the media title may be common to multiple versions ofthe media title. For example, the media title could include a number ofdifferent localized versions to support playback in multiple languages.Each localized version of the media title could include audio content ina corresponding language, as well as one or more scenes of video contentthat show onscreen text, graphics, and/or other types of localization inthe same language. In another example, the media title could includedifferent versions of scenes with sensitive content to meet criteria fordifferent television, film, or content ratings for a given country.

Server application 217 uses one or more file mappings 502 and/or a fileextent index 504 to process request 500. File mappings 502 and/or fileextent index 504 may be stored in a relational database, key-valuestore, distributed filesystem, one or more flat files, and/or anothertype of data store or format.

File mappings 502 include identifiers 512(1)-512(X) for differentversions of the media title. Each of identifiers 512(1)-512(X) isreferred to individually as identifier 512. For example, each identifier512 could include a title, filename, numeric identifier, and/or anothervalue that uniquely identifies the corresponding version of the mediatitle.

File mappings 502 also include paths 522(1)-522(X) for files218(1)-218(X) on system disk 206. Each of paths 522(1)-522(X) isreferred to individually as path 522, and each of files 218(1)-218(X) isreferred to individually as file 218.

More specifically, each of file mappings 502 includes a one-to-onemapping between a given identifier 512 fora version of the media titleand a path 522 for a corresponding file 218 that stores video (oranother type of) content for the media title. Within each file mapping502, identifier 512 acts as a key that can be used to retrieve path 522for a corresponding file 218.

In one or more embodiments, server application 217 processes request 500by performing a lookup of file mappings 502 using identifier 508. Whenidentifier 508 matches a given identifier 512 in file mappings 502,server application 217 retrieves the requested range 510 of data from aparticular file 218 at the corresponding path 522 to which the givenidentifier 512 is mapped. For example, server application 217 couldmatch a value of “111222333” for identifier 508 to the following mappingincluded in file mappings 502:

-   -   111222333/1/01/111222333.ismv        Server application 217 would retrieve a value of        “/1/01/111222333.ismv” for path 522 from the mapping and read        data 524 that spans a byte range 510 (e.g., range of byte        offsets) specified in request 500 from the corresponding file        218 at path 522. Server application 217 would then return the        retrieved data 524 in a response 506 to request 500, thereby        allowing the device (e.g., endpoint device 115) from which        request 500 was received to start or continue playback of the        version of the media title stored in the “111222333” file 218.

Unlike file mappings 502, file extent index 504 includes data that canbe used to perform streaming or playback of a corresponding version ofthe media title from multiple files (or multiple non-contiguous segmentswithin the same file). For example, file extent index 504 could becreated for a version of the media title that includes alternative oradditional scenes, which are substituted for or added to originalversions of the scenes in a “base” version of the media title. In thisexample, the alternative or additional scenes could be stored in one ormore files, and scenes from the base version of the media title could bestored in one or more other files.

As shown, file extent index 504 includes an identifier 514 (e.g., aunique name or alphanumeric identifier) for the version of the mediatitle, metadata 516 related to the version, and mappings of identifiers518(1)-518(Y) for one or more files 218 to ranges 520(1)-520(Y) of datato be retrieved from the file(s) (e.g., a range denoted by a startingbyte offset and an ending byte offset, a range denoted by a startingbyte offset and an end represented by a number of bytes after thestarting byte offset, etc.). Each of identifiers 518(1)-518(Y) isreferred to individually as identifier 518, and each of ranges520(1)-520(Y) is referred to individually as range 520. The ordering ofmappings between identifiers 518(1)-518(Y) and the corresponding ranges520(1)-520(Y) in file extent index 504 additionally reflects the orderin which video content should be retrieved for end-to-end playback ofthe version of the media title.

An example file extent index 504 includes the following representation:

-   -   111222111 1593204284, 46828784, ismv; 111222333:0:20000;        111222444:5000:46808784

The above representation includes a value of “111222111” for identifier514, followed by three metadata 516 values. The first value of“1593204284” represents the modification time for the correspondingversion of the media title, the second value of “46828784” representsthe length in bytes of the version, and the third value of “ismv”represents a filename extension that can be used to construct aHypertext Transfer Protocol (HTTP) response 506 header. Metadata 516values are followed by two mappings of identifiers 518 to ranges 520.The first mapping includes a value of “111222333” for identifier 518, abeginning byte offset of 0 in the corresponding range 520, and a valueof “20000” for the number of bytes spanned by the corresponding range520. The second mapping includes a value of “111222444” for identifier518, a beginning byte offset of “5000” in the corresponding range 520,and a value of “46808784” for the number of bytes spanned by thecorresponding range 520. This example file extent index 504 indicatesthat the first 20,000 bytes of the “111222111” version of the mediatitle are retrieved from the first 20,000 bytes of the file mapped tothe “111222333” identifier in file mappings 502, and that the remaining46,808,784 bytes of the “111222111” version are retrieved starting atthe 5,000th byte of the file mapped to the “111222444” identifier infile mappings 502.

When identifier 508 in request 500 does not match any identifier 512 infile mappings 502, server application 217 may match identifier 508 toidentifier 514 in a given file extent index 504. For example, serverapplication 217 could perform a lookup of a database, key-value store,and/or another data store to retrieve a given file extent index 504 witha value of identifier 514 that matches the value of identifier 508 inrequest 500. This lookup could be performed in conjunction with orindependent of a lookup of file mappings 502 using the same identifier508.

After identifier 508 is matched to identifier 514 in file extent index504, server application 217 uses mappings between one or moreidentifiers 518 to one or more ranges 520 in file extent index 504 andcorresponding file mappings 502 between the same identifiers 512 and thecorresponding paths 522 to retrieve data 524 in the requested range 510.In other words, server application 217 uses file extent index 504 andfile mappings 502 to piece together different ranges of data 524 frommultiple files 218 and return data 524 in response 506 so that, to thedevice from which request 500 was received, the returned data 524appears to be read in a contiguous range from the same file.

The operation of server application 217 is illustrated using a value of“111222111” for identifier 508 in request 500, the above example fileextent index 504, the above example file mapping of“111222333/1/01/111222333.ismv,” and an additional file mapping of“111222444/1/01/111222444.ismv.” First, server application 217 matchesidentifier 508 to the same value of “111222111” for identifier 514 inthe example file extent index 504. Next, server application 217 usesmappings of identifiers 518 to ranges 520 in the example file extentindex 504 to determine one or more files 218 from which the requestedrange 510 of data 524 is to be extracted, as well as correspondingportions of data to be extracted from each file. Server application 217also uses file mappings 502 associated with the file(s) to locate thefile(s) on system disk 206, retrieve the corresponding portions of datafrom the file(s), and return the retrieved data 524 in response 506.

Thus, if range 510 in request 500 includes the first 10,000 bytes of theversion of the media title represented by the “111222111” identifier,server application 217 would use the first mapping in the example fileextent index 504 to determine that the entire range 510 is to be readfrom the first 10,000 bytes of the file mapped to the “111222333”identifier 518 in the example file extent index 504. Next, serverapplication 217 would use the file mapping that includes the “111222333”identifier 512 to obtain a path of “/1/01/111222333.ismv” for thecorresponding file and retrieve the first 10,000 bytes from the file.Server application 217 would then generate response 506 that includesthe retrieved data 524 and transmit response 506 to the device orlocation from which request 500 was received.

If range 510 in request 500 includes 10,000 bytes starting at the20,000th byte of the media title represented by the “111222111”identifier, server application 217 would use the first and secondmappings in the example file extent index 504 to determine that theentire range 510 is to be read from the file mapped to the “111222444”identifier 518 in the example file extent index 504. Next, serverapplication 217 would use the file mapping that includes the “111222444”identifier to obtain a path of “/1/01/111222444.ismv” for thecorresponding file and retrieve 10,000 bytes from the file, starting atbyte offset 5,000 in the file.

If range 510 in request 500 includes 10,000 bytes starting at the100,000th byte of the media title represented by the “111222111”identifier, server application 217 would use the mappings in the examplefile extent index 504 to determine that the entire range 510 is to beread from the file mapped to the “111222444” identifier 518 in theexample file extent index 504. Next, server application 217 would usethe file mapping that includes the “111222444” identifier to obtain apath of “/1/01/111222444.ismv” for the corresponding file and retrieve10,000 bytes from the file, starting at byte offset 85,000 in the file(since the first 20,000 bytes in the media title come from the filemapped to the “111222333” identifier and the starting point for therange from the file mapped to the “111222444” identifier is the 5,000thbyte).

In some embodiments, server application 217 uses segment indexes530(1)-530(X) for one or more files 218(1)-218(X) to process request 500when range 510 is specified in time offsets instead of byte offsets. Forexample, request 500 could include time offsets in range 510 whenrequest 500 is used to “seek” or “scrub” to a different part of themedia title during playback. Request 500 could also, or instead, includetime offsets in range 510 when request 500 is received from a givenplayback application 436 that performs retrieval and playback ofstreaming content using time offsets instead of byte offsets. Each ofsegment indexes 530(1)-530(X) is referred to individually as segmentindex 530 and includes a mapping of time offsets (e.g., timestamps) tobyte offsets in individual segments 532(1)-532(X) within thecorresponding file 218. Each segment index 530 may be stored at thebeginning of the corresponding file 218 and/or in a separate file orlocation.

More specifically, when request 500 includes a range 510 of timeoffsets, server application 217 may match identifier 508 to acorresponding identifier 512 in file mappings 502 and/or identifier 514in file extent index 504. If identifier 508 is the same as a givenidentifier 512 in file mappings 502, server application 217 retrievessegment index 530 from file 218 at a corresponding path 522 to which thegiven identifier 512 is mapped. Server application 217 also usesmappings between time offsets and byte offsets in the retrieved segmentindex 530 to convert the time offsets in range 510 into byte offsets infile 218. Server application 217 then retrieves data 524 spanning thebyte offsets from file 218 and return data 524 in response 506 torequest 500.

If identifier 508 matches identifier 514 in file extent index 504,server application 217 uses file extent index 504 and one or moresegment indexes 530 for one or more files 218 represented by one or moreidentifiers 518 in file extent index 504 to process request 500. Inparticular, server application 217 uses segment indexes 530 to convertranges 520 of byte offsets in file extent index 504 into ranges of timeoffsets for the corresponding files 218. Server application 217 mayoptionally store mappings between byte offsets specified in ranges 520within file extent index 504 and the corresponding time offsets in files218 in file extent index 504 and/or another index structure. Forexample, server application 217 could annotate a given range 520 of byteoffsets in file extent index 504 with a corresponding range 520 of timeoffsets in the version of the media title. After request 500 isreceived, server application 217 may use these ranges 520 of timeoffsets to identify one or more files 218 from which data spanning range510 is to be retrieved. Server application 217 may then use segmentindexes 530 for these file(s) to convert time offsets in range 510 intoone or more ranges of bytes in the file(s), retrieve data 524 spanningthe byte range(s) from the file(s), and return the retrieved data 524 inresponse 506.

The operation of server application 217 is illustrated using the examplefile extent index 504 and example file mappings 502 above, a value of“111222111” for identifier 508 in request 500, and time offsets of0:00:00 and 0:00:30 in range 510 within request 500. First, serverapplication 217 matches identifier 508 to the same value of “111222111”for identifier 514 in the example file extent index 504. Serverapplication 217 also retrieves, from file extent index 504 and/or one ormore segment indexes 530 for the “111222333” and “111222444” files,mappings that convert the byte range starting at offset 0 and spanning20,000 bytes for the “111222333” file to time offsets of 00:00:00 to00:00:30 and the byte range beginning at byte offset 5,000 and spanning46,808,784 bytes for the “111222444” file to time offsets of 00:00:31 to03:00:00. Server application 217 then uses file mappings 502 to retrievethe first 20,000 bytes from the “111222333” file and return theretrieved data in response 506 to request 500.

If request 500 includes the same identifier 508 of “111222111” and timeoffsets of 00:00:00 and 00:01:00 in range 510, server application 217may use the mappings of byte ranges to time offsets in file extent index504 and/or one or more segment indexes 530 to determine that range 510spans both the “111222333” and “111222444” files. Server application 217may retrieve the entire byte range of 0 to 20,000 from the “111222333”file, since the time offsets spanned by the first 20,000 bytes of the“111222333” file fall within the time offsets in range 510. Serverapplication 217 may also retrieve segment index 530 for the “111222444”file and use one or more mappings in the retrieved segment index 530 toconvert the time offset of 00:01:00 from range 510 into a byte offset of45,000 in the “111222444” file. Server application 217 may then generateresponse 506 that includes the first 20,000 bytes from the “111222333”file and additional data spanning the byte offsets of 5,000 and 45,000from the “111222444” file.

FIG. 6A illustrates an exemplar set of data structures that can be usedwhen playing back a version of a media title, according to variousembodiments. As shown, these structures include two files 600-602 and afile extent index 628.

File 600 includes a number of portions 604-612. The first portion 604stores a segment index (SIDX) that maps time offsets in one or moreversions of the media title to byte offsets in file 600, and foursubsequent portions 606-612 store four data segments S1, S2, S3, and S4.Data segments S1, S2, S3, and S4 in portions 606-612 include encodedsegments of video and/or other content in the version of the mediatitle, which can be partially or wholly retrieved and delivered toplayback application 436 on a given endpoint device 115 for playback onthe same endpoint device 115.

Like file 600, file 602 includes a number of portions 622-626. The firstportion 622 stores a SIDX (denoted as SIDX′) that maps time offsets inone or more versions of the media title to byte offsets in file 602, andtwo subsequent portions 624-626 store two data segments S2′ and S4′. S2′includes an alternative version of segment S2, and S4′ includes analternative version of segment S4. For example, segments S2′ and S4′could include localized French versions of English-language videocontent stored in segments S2 and S4, respectively. In another example,segments S2′ and S4′ could include edited or audience-appropriateversions of original video content stored in segments S2 and S4,respectively.

In some embodiments, SIDX′ in portion 622 of file 602 includes mappingsof time offsets in one or more versions of the media title to byteoffsets in one or more corresponding files 600 and/or 602. Thesemappings allow the alternative versions of video content in segments S2′and S4′ to be overlaid onto “base” or original versions of video contentin file 600 during playback of a version of the media title thatreplaces segments S2 and S4 with segments S2′ and S4′, respectively. Forexample, SIDX′ in portion 622 could include mappings of time offsets insegment S1 to byte offsets in portion 606, followed by mappings of timeoffsets in segment S2′ to byte offsets in portion 624, followed bymappings of time offsets in segment S3 to byte offsets in portion 610,followed by mappings of time offsets in segment S4′ to byte offsets inportion 626.

Because text in different languages can consume different amounts and/orregions of screen space in these scenes, alternative versions of videocontent stored in S2′ and S4′ can occupy different amounts of space thanthe original versions stored in S2 and S4, respectively. In particular,byte offsets denoting the boundaries of portions 604-626 in files600-602 are shown in FIG. 6A, and ranges of these byte offsets occupiedby various portions 604-626 are described below. Each range isrepresented by a starting byte offset that is included in the range andan ending byte offset to which the range extends but does not include.Thus, an example range spanned by the byte offsets of 5,000 to 10,000would be interpreted as 5,000 (inclusive) to 10,000 (exclusive).

More specifically, byte offsets occupied by portions 604-626 indicatethat the first 10,000 bytes of files 600-602 are reserved for thecorresponding portions 604 and 622, which allows SIDX mappings and/orother metadata to be stored in these portions. The byte offsets alsoindicate that S1 in portion 606 spans the byte offsets of 10,000 to20,000 in file 600, S2 in portion 608 spans the byte offsets of 20,000to 26,000 in file 600, S3 in portion 610 spans the byte offsets of26,000 to 35,000 in file 600, and S4 in portion 612 spans the byteoffsets of 35,000 to 50,000 in file 600. The byte offsets furtherindicate that S2′ in portion 624 spans the byte offsets of 10,000 to23,000 in file 602 and that S4′ in portion 626 spans the byte offsets of23,000 to 54,000 in file 602. As a result, S2′ and S4′ are about twicethe size of S2 and S4, respectively.

In turn, SIDX mappings stored in the SIDX of portion 604 and SIDX′ ofportion 622 may reflect the different sizes of the correspondingsegments. For example, the SIDX in portion 604 could map time offsets of00:05:00 and 00:07:00 in the media title to the byte offsets of 20,000and 26,000 spanned by S2 in portion 606, while the SIDX in portion 622could map the same time offsets of 00:05:00 and 00:07:00 in the mediatitle to the byte offsets of 10,000 and 23,000 spanned by S2′ in portion624.

File extent index 628 includes a number of portions 630-642, which storedata that can be used to perform streaming or playback of a version ofthe media title from multiple files. For example, file extent index 628could be used to process requests for content in a French version of themedia title, which includes a non-localized English version of a firstscene stored in S1, a French version of a second scene stored in S2′, anon-localized version of a third scene stored in S3, and a Frenchversion of a fourth scene stored in S4′. In another example, file extentindex 628 could be used to process requests for content in afamily-friendly version of the media title, which includes an originalversion of a first scene stored in S1, an edited version of a secondscene stored in S2′, an original version of a third scene stored in S3,and an edited version of a fourth scene stored in S4′.

More specifically, file extent index 628 includes a first portion 630storing a unique identifier for the version of the media title, as wellas a second portion 632 that stores metadata (e.g., modification time,length in bytes, filename extension, etc.) related to the version. Theremaining five portions 634-642 store mappings that specify differentranges of data to be read during playback of the version. As describedabove, each mapping in portions 634-642 may include an identifier for afile, as well as a beginning and ending byte and/or time offset for arange of data that is stored in the file and included in the version ofthe media title. The ordering of the mappings in portions 634-642additionally indicates the order in which video content should beretrieved for end-to-end playback of the version of the media title. Inparticular, the mappings in portions 634-642 specify that end-to-endplayback of the version of the media title should involve retrievingSIDX′ stored in file 602 (e.g., to allow requests for data spanning timeoffsets in the version of the media title to be processed), followed byretrieving S1 stored in byte offsets 10,000 up to (but not including)20,000 from file 600, followed by retrieving S2′ stored in byte offsets10,000 up to (but not including) 23,000 from file 602, followed byretrieving S3 stored in byte offsets 26,000 up to (but not including)35,000 from file 600, and followed by retrieving S4′ stored in byteoffsets 23,000 up to (but not including) 54,000 from file 602.

FIG. 6B illustrates how a request for media content is processed usingthe exemplar set of data structures of FIG. 6A, according to variousembodiments. Request 650 includes a first portion 654 that specifies anidentifier for a version of a media title, a second portion 656 thatspecifies a beginning byte offset of 15,000, and a third portion 658that specifies an ending byte offset of 24,999.

As shown, request 650 is processed by retrieving data spanning the rangerepresented by the beginning and ending byte offsets in portions 656-658from the version of the media title. To process request 650, serverapplication 217 matches the ID in portion 654 to the ID in portion 630of file extent index 628. Next, server application 217 uses file extentindex 628 to identify one or more files from which the range of data isto be retrieved, as well as portions of the file(s) corresponding to therange of data.

In particular, server application 217 uses mappings stored in portions634-642 of file extent index 628 to convert the beginning and endingbyte offsets in portions 656-658 of request 650 into offsets within oneor more files 600-602. First, server application 217 uses the byte rangeof 0 to 10,000 spanned by SIDX′ in the mapping stored in portion 634 andthe byte range of 10,000 to 20,000 spanned by S1 in the mapping storedin portion 636 to determine that the beginning offset of 15,000 inportion 656 of request 650 corresponds to the byte offset of 15,000 infile 600. For example, server application 217 could determine that the15,000th byte of content in the requested version of the media titlelies beyond the 10,000 bytes spanned by SIDX′ in the mapping stored inportion 634. Server application 217 could also determine that this15,000th byte is 5,000 bytes after SIDX′ (e.g., by subtracting the10,000 bytes spanned by SIDX′ from the requested byte offset of 15,000)and add 5,000 to the beginning offset of 10,000 for S1 in the mappingstored in portion 636 to obtain an offset of 15,000 in file 600. Sincethis offset of 15,000 in file 600 falls within the byte range stored inportion 636, server application 217 would retrieve data starting fromthis offset.

Server application 217 also determines that the ending offset of 24,999in portion 658 is 10,000 bytes after the starting offset of 15,000 inportion 656, thereby indicating that 10,000 bytes of content in theversion of the media title are to be retrieved, starting at the 15,000thbyte of content in the version of the media title. Server application217 then uses mappings in portions 634-642 of file extent index 628 toidentify a byte offset in a file that corresponds to 10,000 bytes afterthe 15,000th byte of content. For example, server application 217 coulddetermine that 5,000 bytes lie between the byte offset of 15,000 in file600, which represents the 15,000th byte of content in the version of themedia title, and the end of the byte range stored in portion 636. Serverapplication 217 would then determine that 5,000 more bytes are to beretrieved from one or more byte ranges stored in subsequent portions638-642 of file extent index 628 to satisfy request 650. In turn, serverapplication 217 would use the byte range of 10,000-23,000 spanned by S2′in the mapping stored in portion 638 to determine that the requestedrange ends in S2′ within file 602, and that the remaining 5,000 bytesshould be retrieved from byte offsets 10,000 to 14,999 in file 602.

Server application 217 then generates and transmits a response 652 torequest 650 that includes content spanning the byte offsets of 15,000 to24,999 in the version of the media title. As shown, the responseincludes an optional first portion 660 that includes the same identifieras portions 630 and 654, a second portion 662 that includes 5,000 bytesspanning the byte offsets of 15,000 to 19,999 from S1 in file 600, and athird portion 664 that includes 5,000 bytes spanning the byte offsets of10,000 to 14,999 from S2′ in file 602. Response 652 may additionally beformatted so that the 10,000 bytes of data retrieved by serverapplication 217 appear to be from a contiguous portion of a single file.

FIG. 7 is a flow diagram of method steps for accessing a media title forplayback, according to various embodiments. Although the method stepsare described in conjunction with the systems of FIGS. 1-6, personsskilled in the art will understand that any system configured to performthe method steps, in any order, is within the scope of the presentinvention.

As shown, server application 217 receives 702 a request for a range ofdata included in an encoded version of a media title. For example,server application 217 could receive the request from a client device(e.g., endpoint device 115) that provides streaming media functionalityto an end user. The client device could include a legacy streaming videoapplication, which requests ranges of data from a single file duringplayback of a media title instead of switching between files at certainpoints during the playback. The request could include an identifier(e.g., filename) for the file, a starting time or data offset for therange of data, and an ending time or data offset for the range of data.Alternatively, the request could specify a number of bytes (or seconds)of content to retrieve after the starting offset in lieu of the endingtime or data offset.

Next, server application 217 determines 704, based on a file extentindex, one or more files that are included in a set of files acrosswhich the encoded version of the media title is stored and from whichthe range of data is to be accessed. The set of files may overlap withother sets of files across which other encoded versions of the mediatitle are stored. For example, multiple encoded versions of the mediatitle could include a “base” or “original” version of content stored inone or more files, while each encoded version of the media title couldinclude additional content that is specific to the version in the samefile(s) and/or one or more different files. The file extent indexincludes the identifier for the encoded version of the media title andmetadata related to the encoded version of the media title (e.g., alength of the encoded version, a modification time of the encodedversion, a file extension to be included in a header for a response tothe request, etc.). The file extent index also maps identifiers for theset of files to ranges of data stored in the files. Each range of dataidentifies at least a portion of the corresponding file to be includedin the encoded version of the media title. In addition, the ordering ofmappings between identifiers and the corresponding offset ranges in thefile extent index reflects the order in which video content should beretrieved for end-to-end playback of the encoded version of the mediatitle. Thus, the encoded version may be played from start to finish byretrieving the first range of data included in the first mapping withinthe file extent index from a first file represented by the firstidentifier in the first mapping, followed by retrieving the second rangeof data included in the second mapping within the file extent index froma second file represented by the second identifier in the secondmapping, and so on.

Server application 217 also retrieves 706 the range of data from thefile(s) based on the file extent index and/or one or more segmentindexes for the file(s). More specifically, server application 217 mayuse mappings in the file extent index and/or segment index(es) toconvert a starting offset for the range of data specified in the requestinto a first offset within a file identified in the file extent index.In general, this conversion may be performed via one or morecomputations or comparisons involving the starting offset and the numberof bytes spanned by one or more ranges of data included in the firstfile extent index. After these computations or comparisons areperformed, server application 217 is able to identify the file in whichthe starting offset is found, as well as the first offset in the file towhich the starting offset corresponds.

For example, server application 217 could iteratively perform asummation of the number of bytes spanned by the first n ranges of datain mappings within the file extent index. Once the resulting sum isgreater than the starting offset, server application 217 could identifythe value of n that produced the sum and determine that the startingoffset is located in a file represented by the nth mapping in the fileextent index. Server application 217 could subtract the starting offsetfrom the sum to obtain a “difference” value representing the number ofbytes separating the first offset and the end of the range of data inthe nth mapping. Server application 217 could then subtract the valuefrom the end of the range of data in the nth mapping to obtain the firstoffset in the file from which the range of data specified in the requestis to be retrieved. Alternatively, server application 217 could subtractthe sum representing the number of bytes spanned by the first n−1 rangesof data in the file extent index from the starting offset to obtain avalue representing the number of bytes separating the first offset andthe start of the range of data in the nth mapping. Server application217 could then add the value to the start of the range of data in thenth mapping to obtain the first offset in the file from which the rangeof data specified in the request is to be retrieved.

In another example, server application 217 could iteratively subtractthe number of bytes spanned by each range of data in the file extentindex from the starting offset, so that the nth iteration generates avalue that is the result of subtracting the number of bytes spanned bythe first n ranges of data in mappings within the file extent index fromthe starting offset. Using this iterative process, server application217 could identify the lowest value of n that produces a negative numberand determine that the starting offset is located in a file representedby the nth mapping in the file extent index. Because this negativenumber represents the numerical difference between the first offset andthe end of the range of data in the nth mapping, server application 217could calculate the first offset within the file that corresponds to thestarting offset by summing this negative number and the end of the rangeof data in the nth mapping.

After the starting offset for the range of data specified in the requestis converted into a first offset within a file identified in the fileextent index, server application 217 may retrieve the number of bytesspanned by the range of data from the file and/or one or more otherfiles identified in the file extent index. If the range of dataspecified in the request falls within the range of data in the nthmapping representing the file, server application 217 could retrieve theentire range of requested data from the file, starting at the firstoffset. If the range of data specified in the request does not fallwithin the range of data in the nth mapping representing the file (e.g.,if the requested range of data spans a greater number of bytes than thenumber of bytes separating the first offset and the end of the range ofdata in the nth mapping representing the file), server application 217could retrieve a first portion of the requested range of data from thefirst offset to the end of the range of data in the nth mapping. Serverapplication 217 could retrieve a second portion of the requested rangeof data from the beginning of the range of data in the n+1th mapping tothe end of the requested range of data or the end of the range of datain the n+1th mapping, whichever occurs first. If the end of therequested range of data exceeds the end of the range of data in then+1th mapping, server application 217 could retrieve additional portionsof requested data from files represented by subsequent mappings in thefile extent index until the entire requested range of data is obtained.

When the request received in operation 702 specifies the range of datato be retrieved in terms of time offsets instead of integer offsetsrepresenting displacements of bytes (or other units of data) from thebeginning of the encoded version of the media title, server application217 uses mappings between time offsets and byte offsets in one or moresegment indexes for the file(s) identified in operation 704 to convert afirst time offset delineating the start of the range of data specifiedin the request into a first offset in a file represented by a mapping inthe file extent index. For example, server application 217 could usesegment indexes for all files represented by mappings in the file extentindex to convert ranges of byte offsets in the file extent index intoranges of time offsets for the corresponding files. Server application217 could optionally store these ranges of time offsets in the fileextent index and/or another index structure. Server application 217could then use these ranges of time offsets to identify one or morefiles from which data spanning the range specified in the request is tobe retrieved. Server application 217 could further use one or moresegment indexes for these file(s) to convert a starting and/or endingtime offset in the requested range into a corresponding starting and/orending offset in a file and retrieve data spanning the requestedrange(s) from the file(s).

Finally, server application 217 transmits 708 the range of data in aresponse to the request. For example, server application 217 includesthe retrieved data, an identifier for the encoded version of the mediatitle, a file extension specified in metadata from the file extent indexfor the encoded version, and/or other data or metadata in the response.Server application 217 then transmits the response to the client deviceover a network connection.

Server application 217 may continue processing 710 additional requestsusing operations 702-708. For example, server application 217 couldprocess each request for a version of a media title that is storedacross multiple files (or multiple non-contiguous segments within thesame file) using a file extent index for the version of the media title,one or more file mappings between identifiers for the files andlocations (e.g., paths) of the files, and/or one or more segment indexesfor the files. Using these mappings and index structures, serverapplication 217 could retrieve one or more portions of the range of dataspecified in each request within one or more ranges of offsets mapped toone or more of the files identified in the file extent index.

In sum, different versions of a media title are stored across multiplefiles and/or multiple segments within a given file. Each version of themedia title may include one or more portions of content that arespecific to the version (e.g., localized versions of scenes that include“burned in” text in different languages) and one or more portions thatare shared with other versions of the media title (e.g., a base ordefault version of the media title). A request for a given version ofthe media title includes a range of data to be retrieved from video orother content for the version. This range can be specified in byte (orother data unit) offsets and/or time offsets within the video for themedia title. When the requested version is stored across multiple filesand/or non-contiguous segments, a file extent index for the version isused to retrieve the range of data in the request. The file extent indexmaps identifiers for files that store content for the version to ranges(e.g., specified in byte and/or time offsets) of data spanned by thecontent. The ordering of mappings between identifiers and thecorresponding ranges of data in the file extent index additionallyreflects the order in which video content should be retrieved forstart-to-end playback of the version of the media title. To process therequest, mappings in the file extent index and/or one or more segmentindexes are used to convert one or more offsets that delineate the rangeof data to be retrieved into one or more corresponding offsets withinfiles identified in the file extent index, and data that spans the rangedenoted by the corresponding offset(s) is retrieved from thecorresponding files. The retrieved data is then returned in a responseto the request for playback of the corresponding version of the mediatitle on the client device from which the request was received.

One technical advantage of the disclosed techniques relative to theprior art is that, with the disclosed techniques, duplication of videocontent across multiple versions of a media title is reduced. In thatregard, the disclosed techniques enable a single copy of video contentthat is common to all versions of a given film to be stored, instead ofreplicating identical video content across multiple files. Thus, withthe disclosed techniques, fewer computational and storage resources areconsumed when encoding and storing multiple versions of a media titlefor streaming. Another technical advantage of the disclosed techniquesrelative to the prior art is that the disclosed techniques allow a givenversion of the media title to be created or modified in an efficient,modular manner, unlike prior art approaches that encode and package agiven version of a media title from beginning to end. These technicaladvantages provide one or more technological advancements over prior artapproaches.

1. In some embodiments, a computer-implemented method for accessing amedia title for playback comprises receiving from a client device afirst request for a first range of data included in a first encodedversion of the media title, wherein the first encoded version of themedia title is stored across a first set of files, determining, based ona first file extent index, one or more files that are included in thefirst set of files and from which the first range of data is to beaccessed, wherein, for each file included in the first set of files, thefirst file extent index maps an identifier for the file to a given rangeof data that is both stored in the file and is included in the firstencoded version of the media title, retrieving the first range of datafrom the one or more files, wherein at least a portion of the firstrange of data retrieved from each of the one or more files falls withinthe given range of data that is stored in the file, and transmitting thefirst range of data to the client device in a response to the firstrequest.

2. The computer-implemented method of clause 1, further comprisingreceiving a second request for a second range of data that begins at afirst time offset in the first encoded version of the media title, andretrieving the second range of data based on the first file extent indexand a first segment index for a first file included in the first set offiles, wherein the first segment index maps one or more time offsets inthe first encoded version to one or more offsets in the first file.

3. The computer-implemented method of clauses 1 or 2, wherein retrievingthe second range of data based on the first file extent index and thefirst segment index comprises determining a first offset in the firstfile to which the first time offset is mapped in the first segmentindex, and retrieving, from the first file, at least a portion of thesecond range of data beginning at the first offset.

4. The computer-implemented method of any of clauses 1-3, whereinretrieving the second range of data based on the first file extent indexand the first segment index comprises determining, based on the firstfile extent index, that the second range of data begins in the firstfile and ends in a second file, retrieving, from the first file, a firstportion of the second range of data beginning at a first offset to whichthe first time offset is mapped in the first segment index and ending ata second offset to which a first identifier for the first file is mappedin the first file extent index, and retrieving, from the second file, asecond portion of the second range of data beginning at a third offsetto which a second identifier for the second file is mapped in the firstfile extent index and ending at a fourth offset to which a second timeoffset delineating an end of the second range of data is mapped in asecond segment index for the second file.

5. The computer-implemented method of any of clauses 1-4, furthercomprising receiving a second request for a second range of dataincluded in a second encoded version of the media title, wherein thesecond encoded version of the media title is stored across a second setof files that overlaps with the first set of files, determining, basedon a second file extent index, one or more additional files that areincluded in the second set of files and from which the second range ofdata is to be accessed, wherein, for each additional file included inthe second set of files, the second file extent index maps an identifierfor the additional file to a given range of data that is both stored inthe additional file and is included in the second encoded version of themedia title, and retrieving the second range of data from the one ormore additional files, wherein at least a portion of the second range ofdata retrieved from each of the one or more additional files fallswithin the given range of data that is stored in the additional file.

6. The computer-implemented method of any of clauses 1-5, whereinretrieving the first range of data from the one or more files comprisesconverting a starting offset in the first range of data into a firstoffset in a first file included in the first set of files, andretrieving a first portion of the first range of data from the firstfile, wherein the first portion begins at the first offset in the firstfile.

7. The computer-implemented method of any of clauses 1-6, whereinretrieving the first range of data from the one or more files furthercomprises retrieving a second portion of the first range of data from asecond file, wherein the second portion ends at a second offset in thesecond file that corresponds to an end of the first range of data.

8. The computer-implemented method of any of clauses 1-7, whereinconverting the starting offset in the first range of data into the firstoffset in the first file comprises identifying the first file based onthe starting offset and a number of bytes spanned by one or more rangesof data included in the first file extent index, and calculating thefirst offset based on a difference between the starting offset and thenumber of bytes spanned by the one or more ranges of data.

9. The computer-implemented method of any of clauses 1-8, wherein thefirst set of files includes a first file that includes a first portionof the media title in a first language and a second file that includesthe first portion of the media title in a second language.

10. The computer-implemented method of any of clauses 1-9, wherein thefirst file extent index includes a length of the first encoded versionof the media title.

11. In some embodiments, a non-transitory computer readable mediumstores instructions that, when executed by a processor, cause theprocessor to perform the steps of receiving from a client device a firstrequest for a first range of data included in a first encoded version ofa media title, wherein the first encoded version of the media title isstored across a first set of files, determining, based on a first fileextent index and one or more file mappings between one or more fileidentifiers and one or more file locations, one or more files that areincluded in the first set of files and from which the first range ofdata is to be accessed, wherein, for each file included in the first setof files, the first file extent index maps an identifier for the file toa given range of data that is both stored in the file and is included inthe first encoded version of the media title, retrieving the first rangeof data from the one or more files, wherein at least a portion of thefirst range of data retrieved from each of the one or more files fallswithin the given range of data that is stored in the file, andtransmitting the first range of data to the client device in a responseto the first request.

12. The non-transitory computer readable medium of clause 11, whereinthe instructions further cause the processor to perform the steps ofreceiving a second request for a second range of data that begins at afirst time offset in the first encoded version of the media title, andretrieving the second range of data based on the first file extent indexand a first segment index for a first file included in the first set offiles, wherein the first segment index maps one or more time offsets inthe first encoded version to one or more offsets in the first file.

13. The non-transitory computer readable medium of clauses 11 or 12,wherein retrieving the second range of data based on the first fileextent index and the first segment index comprises determining a firstoffset in the first file to which the first time offset is mapped in thefirst segment index, and retrieving, from the first file, at least aportion of the second range of data beginning at the first offset.

14. The non-transitory computer readable medium of any of clauses 11-13,wherein the first file includes a first segment from which the at leasta portion of the second range of data is retrieved and a second segmentthat stores content included in a second encoded version of the mediatitle.

15. The non-transitory computer readable medium of any of clauses 11-14,wherein the instructions further cause the processor to perform thesteps of receiving a second request for a second range of data includedin a second encoded version of the media title, and retrieving thesecond range of data from one or more additional files included in asecond set of files based on a second file extent index for the secondencoded version of the media title, wherein the second set of filesoverlaps with the first set of files.

16. The non-transitory computer readable medium of any of clauses 11-15,wherein retrieving the first range of data from the one or more filescomprises converting a starting offset in the first range of data into afirst offset in a first file included in the first set of files,retrieving a first portion of the first range of data from the firstfile, wherein the first portion begins at the first offset in the firstfile, and retrieving a second portion of the first range of data from asecond file that follows the first file in the first file extent index.

17. The non-transitory computer readable medium of any of clauses 11-16,wherein converting the starting offset in the first range of data intothe first offset in the first file comprises determining the first filebased on a number of bytes spanned by one or more ranges of dataincluded in the first file extent index, and calculating the firstoffset based on a difference between the starting offset and the numberof bytes spanned by the one or more ranges of data.

18. The non-transitory computer readable medium of any of clauses 11-17,wherein the given range of data is specified in one or more byte offsetswithin the first file extent index.

19. The non-transitory computer readable medium of any of clauses 11-18,wherein the first file extent index includes at least one of a length ofthe first encoded version of the media title, a modification time of thefirst encoded version of the media title, or a file extension.

20. In some embodiments, a computer-implemented method for retrieving amedia title for playback comprises transmitting to a server machine afirst request for a first range of data included in a first encodedversion of the media title, wherein the first encoded version of themedia title is stored across a first set of files, the first range ofdata resides in one or more files included in the first set of files,and, for each file included in the first set of files, a first fileextent index maps an identifier for the file to a given range of datastored in the file, receiving the first range of data from the servermachine in response to the first request, and causing media contentcorresponding to the first range of data to be output for playback.

21. The computer-implemented method of clause 20, further comprisingtransmitting to the server machine a second request for a second rangeof data that begins at a first time offset in the first encoded versionof the media title, wherein the first time offset is mapped to a firstoffset in a first file within a first segment index for the first file,and receiving the second range of data from the server machine inresponse to the second request.

22. The computer-implemented method of clauses 20 or 21, wherein atleast a portion of the second range of data is retrieved from the firstfile beginning at the first offset.

23. The computer-implemented method of any of clauses 20-22, furthercomprising transmitting to the server machine a second request for asecond range of data included in a second encoded version of the mediatitle, wherein the second encoded version of the media title is storedacross a second set of files that overlaps with the first set of files,the second range of data resides in one or more additional filesincluded in the second set of files, and, for each additional fileincluded in the second set of files, a second file extent index maps anidentifier for the additional file to a given range of data stored inthe additional file, and receiving the second range of data from theserver machine in response to the second request.

24. The computer-implemented method of any of clauses 20-23, wherein atleast a portion of the first range of data is retrieved from a firstfile included in the first set of files beginning at a first offsetcorresponding to a starting offset in the first range of data.

25. The computer-implemented method of any of clauses 20-24, wherein thefirst set of files includes a first file that includes an originalversion of a portion of the media title and a second file that includesan alternative version of the portion of the media title.

26. The computer-implemented method of any of clauses 20-25, wherein thealternative version comprises at least one of an edit to the originalversion, a regional version of the portion, or a version that meetscriteria for a content rating.

Any and all combinations of any of the claim elements recited in any ofthe claims and/or any elements described in this application, in anyfashion, fall within the contemplated scope of the present invention andprotection.

The descriptions of the various embodiments have been presented forpurposes of illustration, but are not intended to be exhaustive orlimited to the embodiments disclosed. Many modifications and variationswill be apparent to those of ordinary skill in the art without departingfrom the scope and spirit of the described embodiments.

Aspects of the present embodiments may be embodied as a system, methodor computer program product. Accordingly, aspects of the presentdisclosure may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.) or an embodiment combining software and hardwareaspects that may all generally be referred to herein as a “module,” a“system,” or a “computer.” In addition, any hardware and/or softwaretechnique, process, function, component, engine, module, or systemdescribed in the present disclosure may be implemented as a circuit orset of circuits. Furthermore, aspects of the present disclosure may takethe form of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

Aspects of the present disclosure are described above with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of thedisclosure. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine. The instructions, when executed via the processor ofthe computer or other programmable data processing apparatus, enable theimplementation of the functions/acts specified in the flowchart and/orblock diagram block or blocks. Such processors may be, withoutlimitation, general purpose processors, special-purpose processors,application-specific processors, or field-programmable gate arrays.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present disclosure. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

While the preceding is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A computer-implemented method for accessing amedia title for playback, the method comprising: receiving from a clientdevice a first request for a first range of data included in a firstencoded version of the media title, wherein the first encoded version ofthe media title is stored across a first set of files; determining,based on a first file extent index, one or more files that are includedin the first set of files and from which the first range of data is tobe accessed, wherein, for each file included in the first set of files,the first file extent index maps an identifier for the file to a givenrange of data that is both stored in the file and is included in thefirst encoded version of the media title; retrieving the first range ofdata from the one or more files, wherein at least a portion of the firstrange of data retrieved from each of the one or more files falls withinthe given range of data that is stored in the file; and transmitting thefirst range of data to the client device in a response to the firstrequest.
 2. The computer-implemented method of claim 1, furthercomprising: receiving a second request for a second range of data thatbegins at a first time offset in the first encoded version of the mediatitle; and retrieving the second range of data based on the first fileextent index and a first segment index for a first file included in thefirst set of files, wherein the first segment index maps one or moretime offsets in the first encoded version to one or more offsets in thefirst file.
 3. The computer-implemented method of claim 2, whereinretrieving the second range of data based on the first file extent indexand the first segment index comprises: determining a first offset in thefirst file to which the first time offset is mapped in the first segmentindex; and retrieving, from the first file, at least a portion of thesecond range of data beginning at the first offset.
 4. Thecomputer-implemented method of claim 2, wherein retrieving the secondrange of data based on the first file extent index and the first segmentindex comprises: determining, based on the first file extent index, thatthe second range of data begins in the first file and ends in a secondfile; retrieving, from the first file, a first portion of the secondrange of data beginning at a first offset to which the first time offsetis mapped in the first segment index and ending at a second offset towhich a first identifier for the first file is mapped in the first fileextent index; and retrieving, from the second file, a second portion ofthe second range of data beginning at a third offset to which a secondidentifier for the second file is mapped in the first file extent indexand ending at a fourth offset to which a second time offset delineatingan end of the second range of data is mapped in a second segment indexfor the second file.
 5. The computer-implemented method of claim 1,further comprising: receiving a second request for a second range ofdata included in a second encoded version of the media title, whereinthe second encoded version of the media title is stored across a secondset of files that overlaps with the first set of files; determining,based on a second file extent index, one or more additional files thatare included in the second set of files and from which the second rangeof data is to be accessed, wherein, for each additional file included inthe second set of files, the second file extent index maps an identifierfor the additional file to a given range of data that is both stored inthe additional file and is included in the second encoded version of themedia title; and retrieving the second range of data from the one ormore additional files, wherein at least a portion of the second range ofdata retrieved from each of the one or more additional files fallswithin the given range of data that is stored in the additional file. 6.The computer-implemented method of claim 1, wherein retrieving the firstrange of data from the one or more files comprises: converting astarting offset in the first range of data into a first offset in afirst file included in the first set of files; and retrieving a firstportion of the first range of data from the first file, wherein thefirst portion begins at the first offset in the first file.
 7. Thecomputer-implemented method of claim 6, wherein retrieving the firstrange of data from the one or more files further comprises retrieving asecond portion of the first range of data from a second file, whereinthe second portion ends at a second offset in the second file thatcorresponds to an end of the first range of data.
 8. Thecomputer-implemented method of claim 6, wherein converting the startingoffset in the first range of data into the first offset in the firstfile comprises: identifying the first file based on the starting offsetand a number of bytes spanned by one or more ranges of data included inthe first file extent index; and calculating the first offset based on adifference between the starting offset and the number of bytes spannedby the one or more ranges of data.
 9. The computer-implemented method ofclaim 1, wherein the first set of files includes a first file thatincludes a first portion of the media title in a first language and asecond file that includes the first portion of the media title in asecond language.
 10. The computer-implemented method of claim 1, whereinthe first file extent index includes a length of the first encodedversion of the media title.
 11. A non-transitory computer readablemedium storing instructions that, when executed by a processor, causethe processor to perform the steps of: receiving from a client device afirst request for a first range of data included in a first encodedversion of a media title, wherein the first encoded version of the mediatitle is stored across a first set of files; determining, based on afirst file extent index and one or more file mappings between one ormore file identifiers and one or more file locations, one or more filesthat are included in the first set of files and from which the firstrange of data is to be accessed, wherein, for each file included in thefirst set of files, the first file extent index maps an identifier forthe file to a given range of data that is both stored in the file and isincluded in the first encoded version of the media title; retrieving thefirst range of data from the one or more files, wherein at least aportion of the first range of data retrieved from each of the one ormore files falls within the given range of data that is stored in thefile; and transmitting the first range of data to the client device in aresponse to the first request.
 12. The non-transitory computer readablemedium of claim 11, wherein the instructions further cause the processorto perform the steps of: receiving a second request for a second rangeof data that begins at a first time offset in the first encoded versionof the media title; and retrieving the second range of data based on thefirst file extent index and a first segment index for a first fileincluded in the first set of files, wherein the first segment index mapsone or more time offsets in the first encoded version to one or moreoffsets in the first file.
 13. The non-transitory computer readablemedium of claim 12, wherein retrieving the second range of data based onthe first file extent index and the first segment index comprises:determining a first offset in the first file to which the first timeoffset is mapped in the first segment index; and retrieving, from thefirst file, at least a portion of the second range of data beginning atthe first offset.
 14. The non-transitory computer readable medium ofclaim 12, wherein the first file includes a first segment from which theat least a portion of the second range of data is retrieved and a secondsegment that stores content included in a second encoded version of themedia title.
 15. The non-transitory computer readable medium of claim11, wherein the instructions further cause the processor to perform thesteps of: receiving a second request for a second range of data includedin a second encoded version of the media title; and retrieving thesecond range of data from one or more additional files included in asecond set of files based on a second file extent index for the secondencoded version of the media title, wherein the second set of filesoverlaps with the first set of files.
 16. The non-transitory computerreadable medium of claim 11, wherein retrieving the first range of datafrom the one or more files comprises: converting a starting offset inthe first range of data into a first offset in a first file included inthe first set of files; retrieving a first portion of the first range ofdata from the first file, wherein the first portion begins at the firstoffset in the first file; and retrieving a second portion of the firstrange of data from a second file that follows the first file in thefirst file extent index.
 17. The non-transitory computer readable mediumof claim 16, wherein converting the starting offset in the first rangeof data into the first offset in the first file comprises: determiningthe first file based on a number of bytes spanned by one or more rangesof data included in the first file extent index; and calculating thefirst offset based on a difference between the starting offset and thenumber of bytes spanned by the one or more ranges of data.
 18. Thenon-transitory computer readable medium of claim 11, wherein the givenrange of data is specified in one or more byte offsets within the firstfile extent index.
 19. The non-transitory computer readable medium ofclaim 11, wherein the first file extent index includes at least one of alength of the first encoded version of the media title, a modificationtime of the first encoded version of the media title, or a fileextension.
 20. A computer-implemented method for retrieving a mediatitle for playback, the method comprising: transmitting to a servermachine a first request for a first range of data included in a firstencoded version of the media title, wherein the first encoded version ofthe media title is stored across a first set of files, the first rangeof data resides in one or more files included in the first set of files,and, for each file included in the first set of files, a first fileextent index maps an identifier for the file to a given range of datastored in the file; receiving the first range of data from the servermachine in response to the first request; and causing media contentcorresponding to the first range of data to be output for playback. 21.The computer-implemented method of claim 20, further comprising:transmitting to the server machine a second request for a second rangeof data that begins at a first time offset in the first encoded versionof the media title, wherein the first time offset is mapped to a firstoffset in a first file within a first segment index for the first file;and receiving the second range of data from the server machine inresponse to the second request.
 22. The computer-implemented method ofclaim 21, wherein at least a portion of the second range of data isretrieved from the first file beginning at the first offset.
 23. Thecomputer-implemented method of claim 20, further comprising:transmitting to the server machine a second request for a second rangeof data included in a second encoded version of the media title, whereinthe second encoded version of the media title is stored across a secondset of files that overlaps with the first set of files, the second rangeof data resides in one or more additional files included in the secondset of files, and, for each additional file included in the second setof files, a second file extent index maps an identifier for theadditional file to a given range of data stored in the additional file;and receiving the second range of data from the server machine inresponse to the second request.
 24. The computer-implemented method ofclaim 20, wherein at least a portion of the first range of data isretrieved from a first file included in the first set of files beginningat a first offset corresponding to a starting offset in the first rangeof data.
 25. The computer-implemented method of claim 20, wherein thefirst set of files includes a first file that includes an originalversion of a portion of the media title and a second file that includesan alternative version of the portion of the media title.
 26. Thecomputer-implemented method of claim 25, wherein the alternative versioncomprises at least one of an edit to the original version, a regionalversion of the portion, or a version that meets criteria for a contentrating.